El Nino may not be severe: BoM

A drought-inducing El Nino event is still likely this summer but may not be severe, the Bureau of Meteorology says.

The BoM's latest El Nino Southern Oscillation (ENSO) wrap, released this week, says an El Nino event hasn't fully developed but impacts consistent with an El Nino are already present.

"Several ENSO indicators are currently close to, or exceed, El Nino thresholds," the ENSO wrap said.

"These include tropical Pacific Ocean temperatures, which have now exceeded El Nino levels for a month, and the Southern Oscillation Index, which has remained at or near El Nino levels for three months."

It says other indicators, such as tropical cloud, trade winds and rainfall patterns, have either remained near average or only temporarily approached thresholds.

"This indicates a typical El Nino ocean-atmosphere interaction may not be fully locked in."

The BoM believes there is a 70 per cent chance an El Nino will form by the end of February but the effect may not be severe.

It says the majority of international climate models suggest further warming of the tropical Pacific Ocean is likely.

"If an El Nino is established, models suggest it will be weak, or moderate at most," the wrap said.

El Nino-like effects will occur in Australia whether one is declared or not, the BoM said.

Much of eastern Australia has had a dry spring and the seasonal climate outlook suggests most of the country will have a warmer, drier summer.

An El Nino event occurs when sea surface temperatures in tropical regions of the Pacific Ocean warm significantly, disrupting winds and weather patterns.

This often brings drought to Australia and heavy rain to parts of North and South America.

The last El Nino drought, the Millennium Drought, gripped eastern Australia over the opening decade of this century.